Thin rubber hose and its production method

ABSTRACT

An impermeable rubber hose is thinned for the purpose of reducing weight and costs. A rigid resin film is used as an intermediate layer. When the resin film is gradually rolled up into a cylindrical shape from a planar shape and fed to an extrusion head and rubber is simultaneously extrusion-molded inside and outside the cylindrical film, the film produces a break or a twist to make extrusion molding difficult. It is an object of the present invention to make simultaneous extrusion molding possible even in such a condition.  
     To attain the above object, a thermoplastic resin film ( 5 ) which forms an intermediate layer ( 2 ) and of which the melting point is lower than the vulcanizing temperature is formed in a long belt-shape. Slits ( 7 ) are provided at fixed intervals on the right and left long side sections ( 8, 8 ) of the film ( 5 ) in the longitudinal direction. When the resin film ( 5 ) is fed into an extrusion head ( 10 ) to be rolled up into a cylindrical shape, because both the long side sections ( 8, 8 ) of the film ( 5 ) are formed as weak sections by the slits ( 7 ), the film ( 5 ) adsorbs a strain when bent and is bent in a circle, thereby allowing the right and left long side sections ( 8, 8 ) to overlap at an overlapping section ( 6 ). In this condition, rubber is simultaneously extrusion-molded inside and outside the film and then, vulcanized to weld the overlapping section ( 6 ), thereby eliminating the slits ( 7 ).

This application is a Divisional of co-pending application Ser. No.10/148,416 filed on Jun. 24, 2002 and for which priority is claimedunder 35 U.S.C. § 120. application Ser. No. 10/148,416 is the nationalphase of PCT International Application No. PCT/JP01/05129 filed on Jun.6, 2001 under 35 U.S.C. § 371. The entire contents of each of theabove-identified applications are hereby incorporated by reference. Thisapplication also claims priority of Applications Nos. 2000-301531,2000-301532 and 2000-301533 all filed in Japan on Sep. 29, 2000 under 35U.S.C. § 119.

FIELD OF THE INVENTION

The present invention relates to a method for producing a liquid or gastransportation hose, and more particularly to a method forextrusion-molding rubber inside and outside an intermediate layer whichis formed by rolling up a film made of a resin or the like into acylindrical shape to allow both ends in the bending direction tooverlap.

DESCRIPTION OF THE PRIOR ART

An example of a rubber hose wherein rubber and a resin film arelaminated is disclosed in Japanese Unexamined Patent Publication No. SHO60-113882 in which an inner layer rubber, the resin film serving as anintermediate layer, and an outer layer rubber are extrusion-molded oneby one. Also, in Japanese Unexamined Patent Publication No. HEI7-314610, there is a description of a fluororesin film having excellentpermeability resistance being used alone as the intermediate layer andthis resin film is simultaneously extrusion-molded together with theinner and outer rubber layers. For such simultaneous extrusion molding,a method for feeding a long, belt-shaped resin film into an extrusionhead for rolling up into a cylindrical shape and for extruding rubberinside and outside the resin film is also known.

Further, Japanese Unexamined Patent Publication No. HEI 9-169061discloses that in such a simultaneous extrusion molding, reinforcedfibers such as long belt-shaped knit are rounded into a cylindricalshape to provide an intermediate layer, and inner and outer rubberlayers are simultaneously extrusion-molded, while feeding theintermediate layer into an extrusion head.

When a liquid or gas transportation hose is thinned for the purpose ofreducing weight and costs, an inner layer collapses in a process forweaving a reinforced intermediate layer and a process for coating asubsequent outer layer rubber according to a hose production method ofconventional specifications and molding becomes very difficult. Even insimultaneous extrusion molding in which weaving of the reinforcedintermediate layer is not necessary, when the thickness of anoverlapping section of the reinforced intermediate layer is reduced, thestrength deteriorates and the thickness is limited to about 3.5 mm.

In the extrusion molding method, when the rubber hose is produced usinga resin and a metal film in the intermediate layer for the purpose ofthinning and improvement of permeability, an intermediate layer film isinserted into an extrusion head in a planar ribbon shape, i.e. a longbelt shape. As a result, a strain is generated in the intermediate layerfilm in a process in which the film is finally wound from a conicalshape to a cylindrical shape. Accordingly, if the intermediate layerfilm is made of a material which is soft and not flexible, a break or atwist is produced in the intermediate film layer and the method becomeslimited, inasmuch as the film cannot be extrusion-molded into auniformly cylindrical shape.

It is therefore a first object of the present invention to solve theabove-mentioned problems, to increase the degrees of freedom for bendingduring molding, to provide an impermeable thin rubber hose which is thinand has excellent pressure resistance, and to realize an efficientproduction method of the rubber hose.

When a film made of resin etc. is rolled into a cylindrical shape andfed into an extrusion head, allowing both ends in the bending directionto overlap, wherein rubber is simultaneously extruded inside and outsidethe film, an overlapping section of the film is provided and if thisoverlapping section is vulcanized while opening, there is thepossibility that liquid or gas contained within can permeate outsidethrough this opening to the detriment of the permeability resistance. Toavoid this, the degree of adhesion at the overlapping section must beincreased so as not to generate openings at each step to the completionof the vulcanization. Causes of deterioration of the degree of adhesionby emergence of openings at the overlapping section include:

-   -   1) By using a high elastic modulus film with high rigidity,        softened inner and outer rubber layers directly after extrusion        are deformed to open by restoration of elasticity;    -   2) Displacement of the overlapping section by bending of a raw        rubber hose when mounted on a mandrel for vulcanizing; and    -   3) Generation of a gap in the overlapping section by welding the        overlapping section of which adhesion is incomplete.

The above-mentioned problem is readily caused when the film is too hardto bend. When the bending load (hereinafter simply referred to as “filmbending load) of the film in measurements converted from bending modulusof the film material in the cross-section of which the width is 100 mmand the thickness is 0.05 mm is 400 N or more, it was difficult so farto perform extrusion-molding in a condition in which the film is rolledto allow the end sections to overlap. It was also difficult to performsubsequent operations such as mounting of the hose on the mandrel.

Accordingly, if a thin film with superb flexibility is adopted, thiskind of opening possibility can be eliminated. However, it is difficultto satisfy the permeability resistance and a tear in the film is readilygenerated when used during molding or under high pressure. Accordingly,a film thickness of at least 0.05 mm or more is generally necessary tosatisfy the demands of permeability resistance and pressure resistance.

However, when the film of such a thickness is a thermoplastic resin,because the resin strongly exhibits the properties of elasticity andrigidity as an inherent property, it is difficult to roll the film intoa cylindrical shape so that it serves as an intermediate layer. Eventhough the rolled intermediate layer is formed, the strength of theouter layer rubber is less than the elasticity of the film at the stageof raw rubber hose before vulcanizing, the overlapping section easilyopens due to the elasticity of the film. When the raw rubber hose ismounted on the mandrel for vulcanizing, the overlapping section readilyopens because the stress also acts from the inner surface of the hose.This phenomenon also applies to an inorganic film such as metal.Accordingly, it is extremely difficult to mold vulcanized rubber hose byrolling up the film, which has a fixed thickness and a fixed hardnessnecessary to satisfy the permeability resistance and pressure resistanceperformance, to form an overlapping section, thereby performingsimultaneous extrusion-molding.

Further, when the film is extrusion-molded in a condition in whichvolatile foreign material such as water is adhering to the surface ofthe film, the volatile content expands during a heating process such asvulcanizing. As a result, a foaming phenomenon is generated when therubber and the film adhere or the overlapping section of the film iswelded. Accordingly, there is some possibility that the productperformance will deteriorate. It is therefore an second object of thepresent invention to solve the problems described above and to provide afilm which can be rolled up to form an overlapping section, wherein thefilm serving as an intermediate layer can be simultaneouslyextrusion-molded.

And it is a third object of the present invention to make simultaneousextrusion molding possible using an intermediate layer made of a highelastic material.

In the case where the long belt-shaped resin film is rounded in acylindrical shape, an overlapping section is formed at a part of thecircumferential section in the longitudinal direction. As a result, abar-shaped step resulting from the overlapping section is formed on thesurface of a rubber hose. Accordingly, when the rubber hose is mountedon the other member and secured by a spring clip, the fastening forcebecomes inconstant and as a result, an improved method of securing isrequired to improve the sealing properties or non-ejection properties.Particularly, if a rubber hose is thinned for the purpose of lighteningand miniaturization, this bar-shaped step becomes larger. Also, if theresin film is thickened to improve the barrier properties for permeationof gas or liquid, the step becomes larger. It is therefore a fourthobject of the present invention to provide an improved thin rubber hosein which, even though an overlapping section is formed on anintermediate layer, this does not affect the surface of the rubber hose.

DISCLOSURE OF THE INVENTION

To attain the above first object, according to the present application,a rubber hose having a resin film as an intermediate layer with an innerrubber layer and an outer rubber layer laminated inside and outside theresin film is provided, characterized in that the resin film is composedof a long, belt-shaped film, wherein a weak section is provided inadvance on the long sides of the film and the resin film is rolled upinto a cylindrical shape so that the two long sides overlap. In thiscase, the resin film can be a laminated metal film or reinforced fiberlayer structure.

According to the present invention, a method of producing a thin rubberhose by extrusion molding comprises the steps of feeding a long,belt-shaped resin film which is provided with a weak section on the longsides in advance, to be rolled up and bent into a cylindrical shape sothat the two long sides overlap, extruding rubber inside and outside theresin film for integration and extrude-molding a raw rubber hose ofwhich the intermediate layer is the resin film, and heating the rawrubber hose up to a predetermined temperature for vulcanization.

In this case, the resin film is a thermoplastic resin, wherein theoverlapping section can be vulcanized, and simultaneously, integrallywelded. Further, the weak section can be formed by providing a pluralityof slits or a plurality of punched holes, or by thinning one or both ofthe long side sections which overlap. It is also possible to providethis thinned section in a tapered shape.

The rubber is mixed with a thermoplastic resin, wherein aftervulcanizing the raw rubber hose, this hose can be reheated to themelting temperature of the mixed thermoplastic resin so that apredetermined shape can be provided. As methods for extrusion moldingthe inner and outer rubber layers, there are a construction method forsimultaneously extruding the inner layer rubber and the outer layerrubber inside and outside the resin film, and a construction method forextruding a laminated inner layer rubber film first and then extrudingthe outer layer rubber on the laminated inner layer rubber film. Eithermethod can be adopted.

According to a thin rubber hose and its production method according tothe present invention, when a resin film is rolled up in a cylindricalshape within an extrusion head or the like, because a weak section isprovided in advance on the long sides, a strain in the resin filmgenerated in the rolling-up process is adsorbed by deformation of theweak section. Because even a rigid resin film can be easily bent in thecylindrical shape, simultaneous extrusion molding is possible in auniform shape. In addition, the degrees of freedom for bending at thetime of vulcanizing molding can be increased. Further, sections otherthan an overlapping section of the film also closely contact the innerand outer layer rubbers by reduced pressure adsorption and this closecontact can be maintained until completion of a vulcanizing processwhereby the shape is finally determined. Accordingly, production of athin hose that has been difficult until now is also possible. Further,it is possible to efficiently produce an impermeable rubber hose that isthin and has excellent pressure resistance.

To attain the above second and third objects, a method for producing athin rubber hose which has an intermediate film layer according to thepresent invention is provided, in which an inner layer rubber and anouter layer rubber are extruded inside and outside the intermediatelayer made of film of a substantially cylindrical shape to mold therubber hose, the method comprising the steps of rolling the belt-shapedfilm into a cylindrical shape to allow a pair of edge sections, one oneach side in the lateral direction, to overlap so that an overlappingsection is formed, feeding the film into an extrusion head, andextruding the inner layer rubber and the outer layer rubber inside andoutside the film while decompressing and drawing the overlapping sectioninto the extrusion head.

In this case, there are two methods for feeding the film into theextrusion head: First, the film is rolled from a planar shape to asubstantially cylindrical shape at the inlet of the extrusion head to befed into the extrusion head (hereinafter referred to as “bendingtreatment within the extrusion head”). The second is that the film isshaped into a substantially cylindrical shape in advance in front of theinlet of the extrusion head and is then fed into the extrusion head(hereinafter referred to as “bending treatment outside the extrusionhead”). Further, a construction technique for simultaneously extrudingthe inner layer rubber and the outer layer rubber inside and outside thefilm, and a construction technique for extruding the laminated layer ofthe inner layer rubber and the film, and then extruding the outer layerrubber onto the film can also be adopted.

The film can be composed of a thermoplastic resin or an inorganicmaterial such as a metal, or a laminated structure combining them. Thebending load of the film of which the width is 100 mm and the thicknessis 0.05 mm can be 400 N or more.

The two edge sections overlapping at the overlapping section can betapered so that they are thinned toward the ends in the lateraldirection.

In extrusion molding, the overlapping section can be caused to adhere bydecompressing the overlapping section of the film that was rolled upinto a circular shape. In the extruding molding for forming theoverlapping section on the film, adhesion can be maintained so as to notallow the overlapping section to open within the extrusion head.Accordingly, even such an intermediate layer material that opens unlessdecompressed, simultaneous extrusion molding is possible. Since adhesionof the overlapping section can be continued until vulcanizing iscompleted after extrusion molding, adhesion of the overlapping sectioncan be continued even within a raw rubber hose that is soft at anunvulcanized stage. Even when the raw rubber hose is mounted on themandrel while being bent, it is possible to cause the overlappingsection to not open while maintaining adhesion. It is also possible toprevent generation of a gap at the overlapping section by welding theoverlapping section in an adhering condition.

Accordingly, even though the film bending load is 400 N or more for thefilm of which the width is 100 mm and the thickness is 0.05 mm, which isdifficult in a conventional technique, it is possible to continueoperations without any problems from extrusion molding to subsequentvulcanizing process by decompressing the overlapping section. Inaddition, since parts other than the overlapping section adhere to theinner and outer layer rubber by pressure reduction and adsorption, andthis adhesion can be maintained until completion of the vulcanizingprocess whereby the shape is finally determined, it is possible toproduce a thin hose that has been difficult until now.

Accordingly, it is possible to realize a method with excellent massproductivity, even though a film with a thickness that can satisfy thedemands of reinforcement of heat resistance and pressure resistance, andimprovement of reinforcement and permeability resistance can beprovided. Particularly, a film of a high elastic modulus that has beenimpossible to mold in a conventional technique can be used. Further,since both the resin and inorganic material can be used as the filmmaterial, it is possible to freely choose the material according to thepurpose and performance required.

In this case, if the planar shaped film is processed by bendingtreatment within the extrusion head, it is possible to make theextrusion molding more efficient. Further, if the film is formed into acylindrical shape in advance by bending treatment outside the extrusionhead, processing becomes easier than with the bending treatment withinthe extrusion head and a film with higher rigidity can be used.

If each of a pair of edge sections overlapping at the overlappingsection is tapered so that they are thinned toward each end, steps canbe eliminated or reduced. Accordingly, when the rubber hose is mountedon the other member and secured using a spring clip, compacting(fastening) force becomes constant and as a result, positive fasteningcan be realized to improve the sealing properties and non-ejectionproperties. Even though the edge sections are thinly tapered, adhesioncan be maintained by decompression.

To attain the above-mentioned third object, a method for producing athin rubber hose provided with an intermediate layer according to thepresent invention is provided, in which an inner rubber layer and anouter rubber layer are extruded inside and outside the intermediatelayer of a substantially cylindrical shape within an extrusion head,comprises the steps of forming a pipe serving as the intermediate layerin advance, providing the pipe with a cut line in the axial direction,feeding the pipe into the extrusion head while cutting the pipe open,and rounding the pipe again within the extrusion head to allow the cutline sections (i.e. end sections facing the cut line) to directly orindirectly overlap, thereby forming the cylindrical intermediate layer.

In this case, the intermediate layer can be composed of a thermoplasticresin, an inorganic material such as a metal, or a laminated structurecombining these. Further, a bending load of the intermediate layer canbe 400 N or more for a film of which a width of 100 mm and a thicknessof 0.05 mm. The inner rubber layer and the outer rubber layer can alsobe extruded decompressing and drawing the overlapping section. There aretwo extruding methods: One is a construction technique forsimultaneously extruding the inner rubber layer and the outer rubberlayer inside and outside the pipe, and the other is a constructiontechnique whereby the inner rubber layer and the pipe are firstlaminated and extruded, then the outer rubber layer is extruded onto thepipe. Either technique can be adopted. Further, the intermediate layercan be formed in a bellows-shape, be helically wound, or be providedwith an embossment.

According to the present invention, a pipe serving as an intermediatelayer is formed in advance. This pipe is provided with a cut line in theaxial direction and fed into an extrusion head, cutting the pipe open.The pipe is rounded again within the extrusion head to allow the cutline section to directly or indirectly overlap, thereby forming theintermediate layer of a cylindrical shape. Thus, even a highly elasticmaterial of which the bending load in a width of 100 mm and a thicknessof 0.05 mm which is difficult in a conventional technique is 400 N ormore can be rounded into a cylindrical shape and fed into the extrusionhead. Accordingly, a method can be realized which has excellentproductivity and which can use the intermediate layer of which thethickness can satisfy the demands of reinforcement, such as for pressureresistance and improvement of permeability resistance. Further, sinceeither of the thermoplastic resin and the inorganic material or thelaminated body of these can be used for the intermediate layer material,it is possible to freely choose any of them according to the aimingperformance.

If the overlapping section is decompressed at the time of extrusionmolding, it is possible to allow the overlapping section to adhere.Accordingly, adherence can be maintained so that the overlapping sectiondoes not open within the extrusion head, and simultaneous extrusionmolding becomes possible without opening the overlapping section even inthe case of high elastic material. Further, adherence of the overlappingsection within the raw rubber hose can be maintained even at theunvulcanizing stage after extrusion molding. Even when the rubber hoseis bent to be mounted on the mandrel in the subsequent vulcanizingprocess, it is possible to allow the overlapping section to continuouslyadhere so as not to open the overlapping section. Accordingly, bydecompressing the overlapping section, operations from extrusion moldingto completion of the subsequent vulcanizing process can be performedwithout any problem using the intermediate layer of high elasticity.Sections other than the overlapping section of the pipe are caused toadhere to the inner and outer rubber layers by decompression and drawingand this adherence is maintained until the completion of the vulcanizingprocess whereby a final shape is determined. Thus, it is also possibleto produce a thin hose that would be difficult by a conventionaltechnique. If the intermediate layer is provided with a bellows shape oris helically wound, or is provided with embossment, bending duringmounting of the hose on the mandrel is easy and it is possible to makeopening of the overlapping section more difficult.

To attain the above-mentioned fourth object, according to the presentinvention, a thin rubber hose comprising an inner rubber layer and anouter rubber layer laminated respectively inside and outside a resinfilm serving as an intermediate layer, characterized in that theintermediate layer has a circular cross-section and forms an overlappingsection by allowing a pair of sides which divide the intermediate layerin the circumferential direction to overlap, wherein at least one of thetwo sides forming the overlapping section on the surface side is thinnedto eliminate a step in the overlapping section on the outside. In thiscase, the thinned section can be tapered to reduce the thickness of theside toward one end in the circumferential direction.

Further, a method for producing a thin rubber hose by extrusion moldingcomprises the steps of thinning at least one of two long side sectionsof a long belt-shaped resin film, rounding the resin film to be fed intoan extrusion head so that the two long sides of the resin film overlapto form an overlapping section where no step is produced at least on thesurface side of the two sides, bending the resin film in a cylindricalshape within the extrusion head, and extruding rubber inside and outsidethe resin film.

It is also possible to round a long belt-shapes resin film to allow thetwo long side sections to overlap, form a cylindrical shape which has anoverlapping section where a step is produced at least on the surfaceside of the two sides, eliminate the step on the surface side by asubsequent process, and extrude rubber inside and outside thecylindrical resin film.

According to the present invention, when the resin film is rounded in acylindrical shape or after the resin film is rounded, it is possible toproduce no step at least on the surface of the overlapping section.Accordingly, when a rubber layer is laminated inside and outside thecylindrically shaped resin film to produce a thin rubber hose, no stepis produced resulting from the overlapping section on the thin rubberhose surface.

Accordingly, when the thin rubber hose is mounted on the other memberand secured by a spring clip, the fastening force becomes constant toimprove the sealing properties, wherein it is possible to make itdifficult for the rubber hose to become detached from the other member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a hose product partially cut awayaccording to a first embodiment (FIGS. 1 through 6);

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a view schematically showing an extrusion molding process;

FIG. 4 is a view showing a planar shape of a resin film;

FIG. 5 is a view explaining mounting of a hose on a mandrel in avulcanizing process;

FIG. 6 is a partially expanded cross-sectional view showing a mandrelmounting condition;

FIG. 7 is a perspective view of an intermediate layer according to asecond embodiment (FIGS. 7 and 8);

FIG. 8 is a view showing a resin film in the extended shape;

FIG. 9 is a view showing an entire molding device of a secondembodiment;

FIG. 10 is an enlarged cross-sectional view of an essential part withinan extrusion head;

FIG. 11 is a cross-sectional view taken along the line 11-11 of FIG. 9;

FIG. 12 is a detailed cross-sectional view of the extrusion head;

FIG. 13 is view showing a structure of an overlapping section accordingto a third embodiment;

FIG. 14 is a view showing a joint structure of an overlapping sectionaccording to a fourth embodiment;

FIG. 15 is an end view of an intermediate layer according to a fifthembodiment (FIGS. 15 and 16);

FIG. 16 is an extended perspective view of a resin film;

FIG. 17 is a view showing a structure of a lamination film according toan sixth embodiment;

FIG. 18 is a view showing a joint structure of an overlapping sectionaccording to a seventh embodiment;

FIG. 19 is a view showing a vulcanizing process according to a eighthembodiment;

FIG. 20 is a view showing a cross head construction technique of a ninthembodiment;

FIG. 21 is a view showing the helical winding of a film according to theabove-mentioned construction technique;

FIG. 22 is a partially enlarged cross-sectional view of the helicalwinding;

FIG. 23 is a view schematically showing a molding device of a tenthembodiment;

FIG. 24 is a perspective view schematically showing an extrusion moldingmethod according to the tenth embodiment;

FIG. 25 is a cross-sectional view corresponding to the line 25-25 ofFIG. 23;

FIG. 26 is a view showing a joint structure of an overlapping sectionaccording to an eleventh embodiment;

FIG. 27 is a perspective view of a completed thin hose partially cutaway according to a twelfth embodiment (FIGS. 27 through 30);

FIG. 28 is a cross-sectional view taken along the line 28-28 of FIG. 27;

FIG. 29 is a cross-sectional view showing a condition in which a resinfilm is rounded;

FIG. 30 is a perspective view showing the planar shape of the resinfilm;

FIG. 31 is an end view of an intermediate layer according to athirteenth embodiment (FIGS. 31 and 32);

FIG. 32 is a partial cross-sectional view of an extrusion head accordingto the thirteenth embodiment; and

FIG. 33 is a view showing a fourteenth embodiment for eliminating a stepin a overlapping section.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments of the present invention will now be describedwith reference to the accompanying drawings. As shown in FIGS. 1 and 2,a rubber hose 1 according to the present invention is provided with aninner rubber layer 3 inside an intermediate layer 2 made of a resin filmand an outer rubber layer 4 outside the intermediate layer 2. The rubberhose 1 is obtained by extrusion-molding these three layers at the sametime.

The total thickness of the rubber hose 1 including the intermediatelayer 2, the inner layer rubber layer 3, and the outer layer rubberlayer 4 is about 1.5˜3.5 mm. This is a remarkably thin hose comparedwith a conventional one. In the present invention, a thin hose means onein such a thickness range. It is desirable that the total thickness ofthe intermediate layer 2 be in a range between 0.01 mm and 1.00 mm.

The resin film 5 forming the intermediate layer 2 is rolled up into acylindrical form to provide a partially overlapping section 6. Theoverlapping section 6 is provided in the longitudinal direction with aplurality of slits 7 at predetermined intervals.

The resin film 5 forming the intermediate layer 2 is a thermoplasticresin of which the melting point is between 50° C. and 300° C. Forexample, THV500 and THV610G (trade names of ternary fluororesinmanufactured by Sumitomo 3M Co., Ltd.) or nylon-12 are used. A materialfor such a resin film can be chosen from a resin such as LDPE (lowdensity polyethylene), LLDPE (linear low density polyethylene), HDPE(high density polyethylene), PP (polypropylene), PET (polyethyleneterephthalate), PBT (polybutylene terephthalate), PA6 (polyamide 6),PA66 (polyamide 66), PA11 (polyamide 11), PA12 (polyamide 12), PPS(polyphenylene sulfide), PVDC (polyvinylidene chloride), PVC (polyvinylchloride), PVA (polyvinyl alcohol), ethylene-vinyl alcohol copolymer, orfluororesin (monopolymer, bipolymer, and terpolymer) according to use inview of strength, pressure resistance, permeability resistance, meltingpoint, heat resistance, flexibility resistance, price or the like. Afilm can be manufactured by either of an inflation film molding methodor a T-die molding method, so that multi-layer extrusion is possible foreach molding method. Further, it is possible to laminate separatelyextruded films for molding at a later process.

A rubber material forming the inner rubber layer 3 and the outer rubberlayer 4 can be chosen from NBR (nytril butadiene rubber), SBR (styrenebutadiene rubber), FKM (fluorine-contained rubber), BR (butadienerubber), CR (chloroprene rubber), IIR (isobutylene isoprene rubber), CSM(chlorosulfonated polyethylene rubber), ECO (epichlorohydrine rubber),EPDM (ethylene-propylene-diene rubber), or silicon rubber based ondemand characteristics from the viewpoints of permeability resistance,strength, heat resistance, weather resistance, chemical resistance, oilresistance, cold resistance, hardness, specific gravity, or price. Theinner and outer layers can be manufactured as a structure of up to threelayers by combining the same or separate materials.

FIG. 3 is a view for schematically explaining simultaneous extrusionmolding in which an intermediate layer forming section 11 of anextrusion head 10 is separately shown for the sake of convenience. Inthis figure, a resin film 5 formed in a long, belt-shape is continuouslyfed into the intermediate layer forming section 11 along a feedingdirection A. In this case, the resin film 5 gradually changes its shapefrom the original planar shape B to a conical shape C and then acylindrical shape D when fed into the intermediate layer forming section11.

Namely, the right and left, long side sections 8, 8 relative to thefeeding direction A are overlapped within the intermediate layer formingsection 11 to form an overlapping section 6. The right and left longside sections 8, 8 are rolled up in a circular section to form acylindrical shape D, but first they form a conically shaped section C asan intermediate form for shifting from the planar shape B to thecylindrical shape D in the vicinity of the inlet of the intermediatelayer forming section 11. At the conically shaped section C, both thelong side sections 8, 8 of the resin film 5 are bent in the direction inwhich they come close to gradually form the overlapping section 6.

When the resin film 5 forms the cylindrical shape D within theintermediate layer forming section 11, an inner layer rubber and anouter layer rubber are extruded inside and outside the cylindrical shapeD by the extrusion head 10, wherein a hollow raw rubber hose 12 obtainedby integrally forming these three layers is simultaneousextrusion-molded and exits the extrusion head 11. This raw rubber hose12 is cut to a predetermined dimension and becomes a completed rubberhose product 1 through a vulcanizing process described later.

FIG. 4 shows part of the resin film 5 which is in the planar shape B.Slits 7 are provided by cutting the edge section of the right and left,long side sections 8, 8 in a range, entering inwardly, forming a widthof an overlapping dimension (a) from each edge section of both long sidesections on the right and left side. This overlapping dimension (a) hasa width equivalent to or smaller than that of the overlapping section 6.The structure of the long sided sections 8, 8 forming the slits 7 is onespecific example of a weak section structure.

The slits 7 are formed in such a manner that the inward end section isinclined forward toward the feeding direction A. However, the angle ofinclination is optional, but it can be provided in a range of up to 90°,i.e. in a range up to the perpendicular to the feeding direction A,which is substantially parallel to a short side 9. The slits 7 are alsoformed in the longitudinal direction at regular intervals. If theinterval is b, the slits are alternately arranged to be offset by (½) bon the right and left sides and, in the overlapping section 6, the rightand left slits 7, 7 are arranged to not overlap.

However, the slits can be arranged to overlap at the overlapping section6. In this case, it is effective for the overlapping section 6 to becompletely welded at a vulcanizing temperature. Since the slits aresituated in the same position on the right and left sides, the rawrubber hose 12 can be easily bent when inserted into a mandrel for thevulcanizing process. It is also possible to provide the slits with adifferent angle and length on the right and left sides. The slits 7 withvarious structures can be continuously formed when the resin film 5 ismolded.

Further, when a length obtained by adding one third (⅓) of thecircumferential length (for example, when the inner diameter of a rubberhose is 36.5 mm and the thickness thereof is 3 mm, the added length is41 mm) of the intermediate layer 2 to the circumferential length is setas the maximum width (i.e. short side measurement) of the resin film 5,it is desirable that slits 7 of a maximum length of 40 mm be provided atequal intervals in the longitudinal direction of the resin film 5 onboth sides or one side of the long side sections 8, 8 of the resin film5.

FIGS. 5 and 6 show a vulcanizing process for a raw rubber hose 1 aobtained by such simultaneous extrusion molding. Namely, the raw rubberhose 1 a cut to a predetermined dimension is mounted on a mandrel 19which has a selectively bent shape as a three-dimensional shape and isvulcanized at a predetermined temperature for a predetermined time. Inthis manner, a rubber hose product 1 with a bent shape corresponding tothe mandrel 19 is obtained.

In this case, as shown in FIG. 6, if the mandrel 19 is provided near thebase section 19 a of the mandrel 19 with a taper section 19 b expandingoutward toward the lower section, the end section of the raw rubber hose1 a is also formed with an expanded section 1 b of a tapered shape whichis similar to the taper section 19 b of the mandrel 19. In this manner,it is possible to easily manufacture an expanded hose, to be connectedto the rubber hose, of which the outer diameter is different from theinner diameter of the rubber hose.

Operation of the present invention will now be described. In FIG. 3,since the long sided sections 8, 8 are provided with slits 7, thesesections 8, 8 form weak sections. Accordingly, when a resin film 5 isfed into an intermediate layer forming section 11 along the feedingdirection A, the resin film 5 is deformed to have a conic section Cwhich is an intermediate form for shifting from a planar shape B to acylindrical shape D. Any strain in the resin film 5 generated in thiscase can be absorbed by a change of opening conditions of the slits 7.

Accordingly, even though the resin film 5 is made comparatively thickand rigid without flexibility and extensibility for the purpose ofimproving permeability and pressure resistance, a break or a twist isnot generated in the course of the conic section C, wherein a uniformcylindrical shape can be provided within the intermediate layer formingsection following the conic section C. As a result, since a uniformcylindrical shape can be maintained even during the simultaneousextrusion molding in an extrusion head 10, it is possible to form a thinhose.

Even in the case of woven fabric reinforced cloth which is superior tothe resin film in flexibility and extensibility and of which the clothend section in the overlapping section is originally difficult to breakduring extrusion molding, there is some possibility that the cloth endsection will break if the overlapping width is too great. In the case ofthe resin film which is inferior to the woven fabric reinforced cloth inflexibility and extensibility, it is considered that a break will beeasily generated in the course of bending into a cylindrical shape froma planar shape. However, by providing a weak section such as slits onthe long side sections 8, 8, the resin film can be easily bent and sucha break is easily prevented.

Further, within the intermediate layer forming section 11, the long sidesections 8, 8 on the right and left sides form an overlapping section 6,wherein the slits 7 on the right and left sides do not overlap and arealternately situated in the longitudinal direction. Accordingly,although the slits 7 are provided, it is possible to prevent permeationthrough the slits 7 and to maintain good impermeability that is anobject of the present invention.

In a condition of the raw rubber hose 1 a obtained by such asimultaneous extrusion molding method, at the overlapping section 6 ofthe resin film 5 forming the intermediate layer 2, the long sidesections 8, 8 which overlap are not integrally provided by welding orthe like. Accordingly, some displacement is possible between theoverlapped sections.

However, since the intermediate layer 2 is integrally embedded betweenan inner rubber layer 3 and an outer rubber layer 4, it is possible tomaintain the overlapping section 6 even though there is deformation dueto some displacement or the like. The overlapping measurement (a) (seeFIG. 4) is also set to such a degree that the overlapping section 6 canbe maintained.

When the raw rubber hose 1 a is vulcanized as shown in FIG. 5, the rawrubber hose 1 a can be mounted on the mandrel 19 following the bentshape of the latter since the overlapping section 6 is designed to havea flexible structure for permitting the deformation such asdisplacement.

Next, when the raw rubber hose 1 a mounted on the mandrel 19 isvulcanized at a predetermined temperature, the inner layer rubber layer3 and the outer layer rubber layer 4 are vulcanized and fixed to a bentshape. Since the resin film 5 of the intermediate layer 2 is also meltedat the vulcanizing temperature and then hardened, the upper and lowerlong side sections 8, 8 are integrally welded at the overlapping section6. In this case, since the slits 7 have disappeared to form a singleresin layer, impermeability improves further.

Also, since the slits 7, 7 provided on both the long side sections 8, 8are alternately formed not to overlap at the overlapping section 6, theslits 7 on one side of the long side sections 8, 8 overlap the sectionswhere no slits are provided on the other side at the overlapping section6. As a result, no internal solution permeates through the slits 7.

However, the slits 7, 7 provided on both the long side sections 8, 8 canbe provided in such a position that they overlap at the overlappingsection 6. In this case, the resin film 5 can be easily bent into acylindrical shape compared with the case where the slits are alternatelyprovided. Even though the slits 7, 7 provided on both the long sidesections 8, 8 overlap at the overlapping section 6, the slits 7, 7 aremelted and welded when vulcanized and finally disappear. As a result, nointernal solution permeates through the slit sections.

As shown in FIG. 6, an expanded section 19 b can also be easily formedby a flexible structure at the overlapping section 6. If the raw rubberhose is semi-cured (semi-vulcanized) soon after extrusion to increasethe rubber hardness, the raw rubber hose can be easily inserted into themandrel. The raw rubber hose can also be vulcanized on the mandrel.

Further, if the resin film 5 is formed to have a multilayered structureof two to five layers and the melting point of the resin film of atleast an innermost layer or an outermost layer is lower than thevulcanizing temperature of the raw rubber hose 12, it is possible toweld the overlapping section 6 and slits 7 of the resin film 5 in thevulcanizing process. When a resin of which the permeability resistanceis superior, but the melting point is low, is used, the resin with a lowmelting point can also be used by laminating a resin of which the heatresistance is superior to both sides of the resin of low melting point.

Close contact between the intermediate layer 2 and the inner layerrubber 3 and outer layer rubber 4 at the overlapping section 6 and atsections other than the overlapping section 6 is maintained untilcompletion of molding under pressure reduced during extrusion.Accordingly, it is possible to manufacture a thin hose such as has beendifficult until now. For example, when the film 5 is 0.2 mm thick, it ispossible to set the thickness of the inner layer rubber 3 at 0.8 mm, thethickness of the outer layer rubber 4 at 1.0 mm and the entire thicknessat 2.0 mm. Further, the entire thickness of the inner layer rubber 3,the intermediate layer 2 and the outer layer rubber 4 can be about 3 to500 times as thick as the entire thickness of the intermediate layer 2.However, it is desirable that the entire thickness of the inner layerrubber 3, the intermediate layer 2, and the outer layer rubber 4 beabout 20 times as thick as the entire thickness of the intermediatelayer 2 for the purpose of obtaining a thin hose.

As is obvious from FIGS. 7 and 8, punched holes 7 a are formed at fixedintervals in the longitudinal direction at a section (i.e. anoverlapping section) where the long side sections 8, 8 overlap. Thepunched holes 20 are alternately provided not to overlap on the rightand left sides.

Since it is possible to make the long side sections 8, 8 weak flexiblesections in such a manner, the same function as the slits can beexpected. The punching holes 7 a can also be continuously formed whenthe resin film 5 is molded.

As other examples of the weak section, there are irregularities shown inFIGS. 13 and 14, a step-like thin section shown in FIG. 29, a taperedthin section shown in FIG. 31 and the like. These examples will bedescribed hereinafter.

The principle of a method for molding the rubber hose by the bendingtreatment within an extrusion head is explained by FIG. 9. First, abelt-shaped film 5 is continuously fed to an extrusion-molding machine10 from a raw film roll 17, wherein the film 5 is rolled up into acylindrical shape to be fed to an intermediate passage 12 of anextrusion head 11. The intermediate passage 12 is a passage for feedingthe film 5 and is provided between an intermediate layer forming section13 which is part of the extrusion head 11. An inner passage 14 for aninner layer is provided inside the intermediate layer forming section 13and an outer passage 15 for an outer layer is provided outside theintermediate layer forming section 13. Raw rubber is fed to each passageto form inner and outer layers. These three passages are joined at thejunction 16 a in the vicinity of the inlet of a collective passage 16.The raw rubber passes through the collective passage 16 and is extrudedfrom there as a rubber hose 1 in which three layers are integrallyformed.

By connecting a vacuum pump 18 serving as a pressure reduction device tothe intermediate passage 12, the intermediate passage 12 is reduced to apredetermined level of pressure lower than atmospheric pressure. Thepressure reduction extends to the collective passage 16 through theintermediate passage 12. Accordingly, the inner and outer layers 3, 4are integrally laminated on the intermediate layer 2 by increasing theirdegree of adhesion to the intermediate layer 2. Two vacuum pumps 18 areshown in the figure for the sake of convenience, but the actualintermediate passage 12 is a single ring-shaped passage to which onevacuum pump 18 is connected.

The rubber hose 1 in a condition directly after extrusion molding isperformed as an unvulcanized or semi-vulcanized raw rubber hose 1 a tobe vulcanized later. The extruded raw rubber hose 1 a is cut to apredetermined dimension and vulcanized by a method shown in FIG. 6.

FIG. 10 is an enlarged cross-sectional view for partially explaining anoverlapping section 6 in the vicinity of the junction 16 a of FIG. 9.FIG. 11 is a cross-sectional view taken along line 11-11 of FIG. 9 toshow the condition of the intermediate layer 2 within the intermediatelayer forming section 13. As shown in these figures, the intermediatelayer forming section 13 is tapered toward the junction 16 a and anopening width of an intermediate passage 12 on the outlet side facingthe junction 16 a is about the thickness of the overlapping section 6.

Accordingly, on the outlet side of the intermediate passage 12, theupper and lower films 5, 5 forming the overlapping section 6 are causedto come into close contact by the intermediate layer forming section 13.Since the intermediate passage 12 is decompressed in the pressurereduction direction schematically shown by arrows on a coloredbackground of FIG. 10, pressure between the upper and lower films 5, 5is also reduced at the overlapping section 6 to provide strong adhesiontherebetween. As a result, foreign materials such as volatile matter inthe overlapping section 6 are drawn out and removed. Accordingly, it ispossible to prevent generation of a phenomenon whereby the volatilematter content expands to form bubbles at the time of heating in thesubsequent vulcanizing process.

Further, as shown in FIG. 11, a small space 29 is formed between asection of the film 5 other than the overlapping section 6 and a sectionof the intermediate passage 12 on the exit side. Accordingly, pressureon the junction 16 a shown in FIG. 10 can also be reduced at the sametime by a vacuum pump 18 connected through the space 29 to theintermediate passage 12.

The film 5 is fed into the junction 16 a in a condition in which asection of the upper and lower films 5, 5 at the overlapping section 6is decompressed and caused to adhere, wherein the inner layer rubber 3and the outer layer rubber 4 are integrally formed. Accordingly, evenwith such a hard film 5 whereby the overlapping section 6 does notadhere, it is possible to positively allow the overlapping section 6 toadhere for simultaneous extrusion molding. Since bending treatmentwithin the extrusion head is possible, highly efficient mass-productioncan be realized.

In this case, as is obvious from FIG. 10, a high vacuum condition ismaintained up to the junction 16 a. Accordingly, it is possible toeliminate gas such as air, or foreign materials such as volatile mattercontent, and to allow the inner layer rubber 3 and the outer layerrubber 4 to be integrally formed with the intermediate layer 2 with ahigh degree of adhesion. It is also possible to prevent generation of aphenomenon whereby the volatile material content expands to form bubblesduring heating in the subsequent vulcanizing process. Further, since thehigh vacuum is maintained up to the conjunction 16 a, the outer layerrubber 4 and the inner layer rubber 3 also receive the force in thedirection in which they come close and it is possible to integrally formthem together with high adherence strength.

A raw rubber hose 1 a extrusion-molded in such a manner is cut to thenecessary length after cooling and stored until vulcanization. Adhesionbetween the intermediate layer 2, the inner layer rubber 3 and the outerlayer rubber 4 at the overlapping section 6, and at the section otherthan the overlapping section 6, is maintained under the reduced pressurewhen extruded. No treatment is given to the hose end surface aftercutting, but since the rubber of the inner and outer layer apply bearingstress to the film contacting surface, no phenomenon whereby theatmosphere or a water content permeates into the overlap of the filmoccurs. The adhering condition at the overlapping section can bemaintained even during storage of the raw rubber hose.

As shown in FIG. 6, adhesion of the overlapping section 6 underdecompression is maintained until vulcanizing is completed. It istherefore possible to prevent displacement or opening of the overlappedsection between contacting surfaces. Further, when the overlappingsection 6 is welded at the vulcanizing temperature by vulcanizing aftermounting on the mandrel 18, no gap is produced at the overlappingsection 6 because adhesion is maintained. Since the overlapping section6 is completely integrated from that point, permeability resistance andpressure resistance can be favorably maintained.

Accordingly, even though a hard film is used which can satisfypredetermined demands such as high permeability resistance and pressureresistance which are required, for example, in a fuel hose, simultaneousextrusion molding can not only satisfy permeability resistance, pressureresistance or the like, but also provide a method that has excellentmass-productivity.

Table shows the relationship between the film bending load and thecondition of the overlapping section in the process from extrusionmolding to vulcanizing, wherein a ◯ is marked when the overlappingsection did not open and an X is marked when it opened. A comparativeexample 1 shows a case where bending treatment within the extrusion headwas performed without pressure reduction. An embodiment 1 is a casewhere the bending treatment within the extrusion head was performed whenpressure was reduced to the negative pressure of 98658 Pa (namely 740mmHg) below the atmospheric pressure. As is obvious from this Table, inthe comparative example 1, when the film bending load is 400 N or more,the result was X (not suitable), but in the embodiment 1, processingbetween 5000 N and 10000 N is possible. This means that a hard filmhaving high bending modulus, i.e. the strong elasticity and rigidity, inother words, a hard film that can attain high permeability resistanceand pressure resistance, can be used.

An embodiment 2 in FIG. 1 is an example using the bending treatmentoutside the extrusion head where the film 5 is shaped to be bent in alateral direction in advance by a means other than the extrusion head infront of the inlet of the extrusion head 11. Comparison with theembodiment 2 will be described hereinafter. TABLE Comparative Filmbending load (*) example Embodiment 1 Embodiment 2  250 N ο ο ο  400 N Xο ο  5000 N X ο ο 10000 N X X ο 20000 N X X οο: No opening formed at overlapping section;X: Opening formed at overlapping section.(*): Film bending load is a measure converted from bending modulus ofthe film material in the cross section of which the width is 100 mm andthe thickness is 0.05 mm.Molding ConditionsComparative example: Bending treatment within extrusion head, molded atatmospheric pressure.Embodiment 1: Bending treatment within extrusion head, molded at 98658Pa (740 mm Hg) below the atmospheric pressure.Embodiment 2: Bending treatment outside extrusion head, molded at: 98658Pa (740 mm Hg) below the atmospheric pressure.

FIG. 12 is a cross-sectional view showing one specific example of theextrusion head 11. As is obvious from this figure, the front end of theextrusion head 11 is provided with a core 20 and a die 21 surroundingthe periphery of the core 20. Provided between the outer circumferenceof the core 20 and the inner circumference of the die 21 is a circularslit 22 for extruding the rubber hose 1. The circular slit 22 isconcentrically provided with the outer circumference of the core 20 andthe inner circumference of the die 21.

The outer circumferential surface of the core 20 and the innercircumferential surface of the die 21 are respectively provided withlinear cross-sectional sections 23, 24 parallel to the extrusion axis C.Each rear section of the linear cross-sectional sections 23, 24continuously extends to an ascending slope 25 which inclines to expandoutwardly relative to the extruding direction A and a descending slope26 which inclines inwardly.

Provided within a space formed to expand backward between the ascendingslope 25 and the descending slope 26 are a substantially cylindricalouter cylindrical section 27 of which the top is tapered off and aninner cylindrical section 28 of which the top is tapered in theexpanding direction and which is provided concentrically inside theouter cylindrical section 27. The outer cylindrical section 27 and innercylindrical section 28 form an intermediate layer forming section 13.The outer cylindrical section 27 is provided with an outer peripheralslope 30 and an inner peripheral slope 31. The outer peripheral slope 30is arranged to face the descending slope 26 leaving a spacetherebetween, and an outer passage 15 of which the top is tapered offrelative to the extruding direction A is formed between the outerperipheral slope 30 and the descending slope 26.

The inner cylindrical section 28 is provided with an outer peripheralsurface 32 of a straight cross-section and an inner peripheral slope 33.The outer peripheral surface 32 forms an intermediate passage 12 ofwhich the top is tapered off relative to the extrusion direction Abetween itself and the inner peripheral slope 31 of the outercylindrical section 27. The inner peripheral slope 33 is arranged toface the ascending slope 25 leaving a space therebetween and forms aninner passage 14 of which the top is tapered off relative to theextrusion direction A.

Reference numeral 34 in the figure is a back joint which forms a part ofthe inner passage 14 and concentrically holds the outer cylindricalsection 27 and the inner cylindrical section 28. The back joint 34 alsosupports the core 20 through an axial center section rod 35. Referencenumeral 36 is a casing for supporting the die 21.

FIG. 13 is a third embodiment relating to a structure of the overlapingsection. In FIG. 13A, lattice-shaped grooves 40 are provided on at leastthe overlapping section which are freely bendable. Irregularities suchas embossment may be provided in place of the grooves 40. In FIG. 13B,wave-shaped irregularity consisting of recesses 41 and convex sections42 extending in the vertical direction (in the longitudinal directionparallel to the long side sections) are provided. With thisconstruction, the resin film 5 is easily bent at the recesses 41.

FIG. 14 shows a fourth embodiment relating to an overlapping section 6,in which rough surfaced sections 45 consisting of a minute recessedsection or convex section, or of irregular sections are formed at anoverlapping section of both end sections on the long sides using asurface roughening method. Since friction at the overlapping section 6is increased by the rough surfaced sections 45, displacement is noteasily caused. As the surface roughening method, there are a suitablemechanical method such as shot-blasting, a method for roughening asurface by chemical treatment and the like. The rough surfaced sectionis also allowed to be the weak section.

FIG. 15 is an end view of a resin film 5 which is formed in acylindrical shape according to a fifth embodiment and FIG. 16 is anextended perspective view of the resin film 5. As is obvious from thesefigures, a metal film 50 is laminated to the resin film 5 to provide alaminated structure, wherein the metal film 50 is arranged to faceinside. Both films are bonded at an overlapping section 6 by a suitableadhesive. However, if the metal film 50 is integrally embedded in theresin film 5, it is possible to integrally form the overlapping section6 by welding.

Such a laminated structure can be provided in various manners, in whichthe resin film 5 can be a multilayered structure of from two layers to amaximum of about five layers. As a result of the multilayeredstructuring, characteristics of different resins can not only becompensated for, but also generation of pinholes in the resin filmproduction process can be reduced. The entire thickness of themultilayered structure exhibits the same performance as a single layerfilm and can be further thinned.

The resin film 5 of such a multilayered structure includes for example,a resin single layer such as a fluororesin (monopolymer, bipolymer, andterpolymer), PVDC, PVC, PVA, PPS, PET, PBT, PA6, PA66, PA11, PA12, PP,HDPE, LLDPE, LDPE, or an ethylene-vinyl alcohol copolymer, or a resinlaminated body consisting of two to five layers made of differentmaterials; a single body of metal sheet alone such as aluminum or alaminated body consisting of two to six layers made of the above resinand an aluminum sheet. In addition, there is another laminated body inwhich a laminated body consisting of two to six layers in whichaluminum, alumina, or silica has been deposited on the above resinsingle layer or the laminated body is treated as a film intermediatelayer, wherein a fiber-reinforced layer such as aramid-fiber, PA6, PA66,PET, PBT, PPS or PVA is added to the inner layer hose side of the filmintermediate layer.

In this laminated body, it is desirable that at least an innermost oroutermost resin layer be constructed using a resin of which the meltingpoint is lower than the vulcanizing temperature and the entire thicknessof the intermediate layer 2 be in a range of 0.01 mm to 1.00 mm.

Reinforced cloth can be added to the intermediate layer for improvementof pressure resistance and can be chosen from aramid-fiber, PA6, PA66,PET, PPS, PVA, or the like depending on use. A main role of thereinforced cloth is to maintain the pressure resistance, but it isdesirable that fibers with excellent performance relating to strength,heat resistance, flexing resistance, absorptivity, resistance, orhydrolytic resistance be used.

There are various weaving structures for fibers such as raschelknitting, plain weave or the like. Wherein, a weaving structure isdesirable which is thin and has the pressure-resistance performance andof which change of outer diameter are small. When the resin or metalfilm and the fiber-reinforced layer are laminated, it is desirable thatthey be laminated in advance for use. When the resin or metal film andthe fiber-reinforced layer are extruded without lamination, moldingfailure or breaking of the film layer due to displacement between thefilm and the reinforced cloth is easily generated. The laminationstructure of a laminated body of the resin or metal film and thefiber-reinforced layer consists of two layers to a maximum of about sixlayers.

If the thickness of a rubber layer is simply reduced for the purpose ofthinning of the hose, the amount of permeation increases in a forminversely proportional to the reduction. Factors such as rubber materialand kind of internal solution, thickness of material and gaspermeability of material, atmosphere temperature, internal pressure andthe like affect the permeation of the contents. Material factors foraffecting the gas permeability include polarity, degree ofcrystallinity, orientation, crystal structure and the like. A resin isgenerally better than rubber for gas permeability for the samethickness, except fluorocarbon rubber. To make the best use of the gaspermeability resistance of the film, it is desirable that the entirethickness of a film laminated body and/or a laminated body of the filmand the fiber-reinforced cloth be 0.01 mm˜1.00 mm. If the thickness islarger than 1.00 mm, even though the slits are provided, it is difficultto mold the film in a cylindrical shape during extrusion. This alsoaffects flexing properties of the hose and conflicts with thinning ofthe hose.

When a rubber layer of hose with a reinforced cloth is thinned,compressive strength, pressure resistance and durability tend todeteriorate and it is obvious that not only the reinforced cloth, butalso tensile strength and elastic modulus of the rubber layer itselfhave a great influence on the strength of the hose. When the rubberthickness of a hose with the reinforced layer is reduced, the amount ofdeformation when stress is applied increases. Accordingly, in such acondition in which repeated stress is applied, pressure resistance,durability and strength deteriorate. When the rubber layer is thinned,sealing properties also deteriorate.

Permeability of a rubber hose with the reinforced cloth in theintermediate layer substantially depends on the material and thicknessof the rubber layer and a degree of contribution by the reinforced clothto permeability is low. Permeation is a phenomenon of penetration anddiffusion of the contents in the rubber layer in a micro-level field,wherein the contents easily pass through a gap in the reinforced clothcomposed of yarn. On the other hand, when the resin film is added to thereinforced cloth, the film functions as a barrier layer in a micro-leveland as a result, permeability remarkably improves. Further, if the resinfilm is laminated with an inorganic material such as aluminum or ceramicor deposited film is used, complete impermeability of inner solution orinner gas is realized.

A thermoplastic resin film is stretched and oriented in all directionsin the manufacturing process, but has creep characteristics.Accordingly, if a stress load is continuously applied for a long time,there is some possibility that deformation is caused. If orientation isintensified, tensile strength in the orientation direction increases,but, on the contrary, tear resistance and pinhole resistancedeteriorate. It is therefore necessary to use a resin that has excellentpressure resistance and heat resistance in a predetermined thickness inthe intermediate film layer. However, by adding one fiber-reinforcedlayer, it is possible to improve the pressure resistance, thinning thefilm layer. Because the reinforced cloth has a weaving structureobtained by twisting a single yarn which is strongly stretched andoriented in the longitudinal direction, the stress in a predeterminedrange can be retained by stretching deformation of the weaving structureitself and any stress greater than the predetermined range can beretained by the tensile strength of the yarn itself.

FIG. 17 shows an sixth embodiment adopting a laminated film, in whichresin films 51, 52, of which the orientation direction and thestretching direction meet at right angles, are laminated. In thismanner, the laminated film can be easily bent to form a cylindricalshape or bent in the longitudinal direction after forming thecylindrical shape, wherein sufficient strength can be secured.

FIG. 18 shows a seventh embodiment relating to the joint of anoverlapping section 6, in which an adhesive agent layer 53, which hasexcellent fuel oil resistance characteristics, is inserted between theoverlapping sections. In this manner, better sealing can be providedagainst permeation of the fuel oil by the adhesive agent layer 53. Ifthe adhesive agent layer 53 is a hot melt type, this is convenientbecause adhesion is made at the same time as joining the overlappingsection 6 by heat welding.

To improve workability after extrusion molding in the case where thefilm of high bending modulus is used, it is possible to use a mixture of2˜30 parts by weight of a thermoplastic resin to 100 parts by weight ofa rubber material. Resins for mixing can be chosen from PP, PBT,polymethyl pentene, PS or the like.

In this manner, if the resin in the rubber material is non-compatiblewith the rubber, the resin remains contained in the rubber even aftervulcanizing. Since the resin in the vulcanized rubber has the propertyof thermoplasticity, it exhibits plasticity if the temperature isgreater than the softening point. On the other hand, the vulcanizedrubber, once vulcanized, does not lose the property of rubberelasticity. Now, by mixing the rubber with the thermoplastic resin, ifthe vulcanized rubber is heated again to the softening point aftervulcanizing to deform and then cooled, it can retain its shape afterdeformation. Deformation can be eliminated if heated again.Specifically, the rubber is semi-vulcanized directly after extrusion toincrease the rubber hardness so that it can be easily mounted on themandrel. The rubber is fully vulcanized after mounting on the mandrel.

Thus, it is possible to improve the problems of rubber hose productivityby reducing various problems such as creases or twists at the bent Rsection, collapse of the end surface, or adherence of work glove markson the hose surface generated when the hose is mounted on the mandrel.

FIG. 19 shows a eighth embodiment in which the composition of the rubberhas been changed. An inner rubber layer and an outer rubber layeraccording to the present embodiment are mixed with a thermoplasticresin. An intermediate layer described in the previous embodiments isselectively used. In such a material composition, a raw rubber hose 1 ais extruded and then vulcanized. The vulcanized hose is mounted on amandrel 19 and heated close to the melting temperature of thethermoplastic resin and then cooled.

Thanks to softening of the thermoplastic resin, the hose follows theshape of the mandrel 19 by and is bent to that shape. This bent shape isset through the subsequent cooling. In this manner, even thoughvulcanization is preceded, the subsequent shaping is possible. Since theoverlapping section can be stabilized by vulcanization, even though thehose is freely bent at the mounting stage on the mandrel 19, it ispossible to maintain the intermediate layer in the cylindrical shape.

As a composition example, the mixture of 2˜30 parts by weight of thethermoplastic resin such as PP, PBT, Polymethyl pentene or PS(polystyrene) to 100 parts by weight of rubber material is possible. Byusing this mixture, it is possible to further improve workability andperformance of the rubber hose.

If the thermoplastic resin in the rubber material is non-compatible withthe rubber, the resin content remains contained in the rubber even aftervulcanization. Since the resin in the vulcanized rubber has the propertyof thermoplasticity, it exhibits plasticity if the temperature isgreater than the softening point. Accordingly, the vulcanized rubber,once vulcanized, does not lose the property of rubber elasticitypermanently. However, if the vulcanized rubber is heated again tore-deform after vulcanization and then cooled, it can retain the shapeafter re-deformation. Re-deformation can be eliminated if heated again.

A rubber hose according to the present invention can also be molded by acrosshead construction method. A ninth embodiment relating to thecross-head method will now be described. In FIG. 20, an inner layerextruder 60 and an outer layer extruder 61 are connected to a head 62from the perpendicular direction. A supply section 63 of a resin film 5is provided at the intermediate section of the head 62 which isconnected to the inner layer extruder 60 and the outer layer extruder61.

The head 62 is constructed as shown in an expanded view, in which theinner layer extruder 60 extrudes an inner layer rubber 3 from an innerlayer rubber passage 65 to the periphery of an inner core 64. The resinfilm 5 of a tape shape which is supplied from the film supply section 63is helically wound around the inner layer rubber 3 (see FIG. 21). Theouter layer extruder 61 extrudes an outer layer rubber 4 from an outerlayer rubber passage 66 on the inner layer rubber 3 for lamination. Inthis manner, a desirable hose 1 a is obtained.

Thus, the film 5 can be helically wound around the rubber using thecross-head construction method. As shown in FIG. 22, the resin film 5forms an overlapping section 6 around the inner layer rubber 3 in thelongitudinal direction. By vacuum-sucking the overlapping section 6through the film supply section 63, adsorption is performed and closecontact can be maintained. FIG. 21 shows the condition in which theresin film 5 is wound around the inner layer rubber 3 and FIG. 22 is apartially expanded cross-sectional view showing the winding operation

Next, a tenth embodiment relating to the bending treatment outside theextrusion head will be described.

As shown in FIGS. 23 and 24, the intermediate layer 2 is formed as apipe 70 which has been obtained in advance by extrusion-molding a highelastic material as outlined below by separate equipment. The pipe 70 iscut by a cutter 71 in the axial direction to provide a slit-shaped cutline 72 to be opened laterally. Opposing ends 78, 78 of the cut line 72are opened to provide a C-shaped cross-section. The pipe 70 iscontinuously fed into an extruder 10 in such a condition, wherein thepipe 70 is rounded again into a cylindrical shape to allow the opposingends 78, 78 to overlap to form an overlapping section 6. The pipe 70 isthen fed into an intermediate passage 12 of an extrusion head 11 whileforming the overlapping section 9. The pipe 70 and the intermediatelayer 2 are the same, but a section before extrusion molding isespecially referred to as the pipe 70. The extruder 10 shown in FIG. 23has a same structure as one in the above-mentioned embodiment.

FIG. 25 is a cross-sectional view corresponding to the line 25-25 ofFIG. 23. The inner cylindrical section 80 is integrally provided, atpart of the outer peripheral section, with a larger diameter section 81which projects outward in the radial direction. The outer peripheralsurface of the larger diameter section 81 closely contacts the innerperipheral slope 83 of the outer cylindrical section 82 and can beconcentrically supported on the inner side of the outer cylindricalsection 82, wherein the intermediate passage 12 has a C-shapedcross-section. Part of the outer peripheral section of the outercylindrical section 82 is also integrally provided with a largerdiameter section 84 which projects outward in the radial direction. Theouter peripheral surface of the larger diameter section 84 closelycontacts an inner peripheral slope of an outer ring 85, wherein an outerpassage 15 has a semi-circular arch shape. Reference numeral 86 in FIG.25 is a back joint which forms part of the inner passage 14 andconcentrically holds the outer cylindrical section 82 and the innercylindrical section 80. The back joint 86 also supports the core 20 (seeFIG. 12) through an axial center road 86.

A production method for a hose made of various materials as outlinedabove will now be described in detail. FIG. 24 is a view forschematically explaining simultaneous extrusion molding according to thepresent invention in which an intermediate layer forming section 11 ofan extrusion head 10 is separately shown for the sake of convenience. Inthis figure, a pipe 70 previously extrusion molded to have a circularcross-section is continuously fed into the intermediate layer formingsection 11 along a feeding direction A while being cut by a cutter 71 toprovide a cut line 7.

In this case, in front of the intermediate layer forming section 11, theopposing cut sides 78, 78 of the pipe 70 are opened to provide asubstantially C-shaped cross-section as in the intermediate passage 12of a C-shaped cross-section shown in FIG. 25. Thus, the pipe 70 can beinserted into the intermediate passage 12 even though the innercylindrical section 80 has the larger diameter section 81. After passingthrough this larger diameter section 81, the pipe 70 is rounded againinto a circular cross-section within the intermediate layer formingsection 11 to allow the opposing ends 78, 78 to overlap to provide theoverlapping section 6. Since the pipe 70 tends to maintain the circularcross-section from its inherent structure, it readily forms theoverlapping section 6 and makes it difficult to open.

In this manner, after the pipe 70 is first cut open, the pipe 70 isrounded again into a substantially circular cross-section within theintermediate layer forming section 11. Then, the inner rubber layer 3and the outer rubber layer 4 are extruded inside and outside the pipe 70and a hollow rubber hose 1 obtained by integrally molding these threelayers is simultaneously extrusion-molded and then extruded from theextrusion head 10.

Since the intermediate layer is formed as the pipe 70 which tends to berestored to its original shape within the intermediate passage 12, it ispossible to readily form the overlapping section 6. A small space 29 isformed between a section of the pipe 70 other than the overlappingsection 6 and a section of the intermediate passage 12 on the exit side(see FIG. 11). Accordingly, the pressure up to the junction 16 a shownin FIG. 23 can be reduced in a single operation by a vacuum pump 18connected through the space 29 to intermediate passage 12.

The pipe 70 serving as the intermediate layer is fed into the junction16 a in a condition in which a section of the upper and lower opposingsides 78, 78 at the overlapping section 6 is decompressed and caused toadhere, wherein the inner rubber layer 3 and the outer rubber layer 4are integrally molded. Accordingly, even with a pipe 70 of such ahardness that the overlapping section 6 is not caused to adhere, it ispossible to positively allow the overlapping section 6 to adhere forsimultaneous extrusion molding. In addition, highly efficientmass-production can be realized.

In this case, as is obvious from FIG. 23, a high vacuum condition ismaintained up to the junction 16 a. Accordingly, it is possible toeliminate gas such as air, or foreign materials such as volatile matter,and to allow the inter rubber layer 3 and the outer rubber layer 4 to beintegrally molded with the intermediate layer 2 with a high degree ofadhesion. It is also possible to prevent generation of a phenomenonwhereby the volatile matter expands to form bubbles during heating inthe subsequent vulcanizing process. Further, since the high vacuum ismaintained up to the junction 16 a, the outer rubber layer 4 and theinner rubber layer 3 also receive the force in the direction in whichthey come close and it is possible to integrally mold them together withhigh adhesion strength.

As is described above, by molding the intermediate layer 2 into the pipe70 in advance, even the highly elastic material can be rounded and fedinto the extrusion head 10. As shown in FIG. 25, even though theintermediate passage 12 of the extrusion head 10 is constructed to havea C-shaped cross-section, the pipe 70 can be fed into the extrusion headby cutting the pipe 70 open in the C-shaped cross-section.

In this manner, it is possible to use the film with a high bendingmodulus. Namely, in the embodiment 2 in Table 1, an embodiment is shownin which such a bending treatment outside the extrusion head is adopted,wherein pressure has been reduced to 98658 Pa (740 mmHg) belowatmospheric pressure. As is obvious from this Table, processing up to20000 N of the film bending load is possible and the film of highbending modulus can be used. When pressure is largely reduced as shownin the embodiment, it is possible to eliminate gas such as air orforeign materials as volatile matter and it is difficult for thevolatile matter to expand to form bubbles during vulcanizing or thelike.

Moreover, in the case of bending treatment within the extrusion head,even though the extrusion head 11 is decompressed, the limit of theadhesion effect of the film is between 5000 N and 10000 N at the most.However, if bending treatment outside the extrusion head is performedand pressure is reduced, this means that it is possible to process up to20000 N. If the film is shaped into the cylindrical shape in advance,processing is easier than with the bending treatment within theextrusion head. Since the film of a high bending modulus after extrusionacts to maintain the cylindrical shape, this also helps improveworkability.

When such a high bending modulus film is used, it is desirable thatflexing be improved during mounting of the rubber on the mandrel and inthe hose product. For such a purpose, when the film is shaped into thecylindrical shape, by providing irregularities extending in thecircumferential direction, it is effective to make the entire section orpart thereof a bellows-shape.

After forming the film in the cylindrical shape in advance, the film canbe processed also by blow molding or the like to form a circularirregularity on the circumference in the circumferential direction. Ifthe irregularity is continuously provided in the longitudinal directionto provide a bellow shape, it is also possible to freely bend the filmin the longitudinal direction.

FIG. 26 shows a eleventh embodiment relating to an overlapping sectionformed by the bending treatment outside the extrusion head. According toone example shown in FIG. 26 (A), the opposed sections 78, 78 do notoverlap directly and both ends thereof are arranged to face one anotherwith a gap 79 between. A separate seal piece 77 is positioned to bridgethe gap 79 and is integrally welded to both the long side sections. Inthis manner, it is possible to provide an intermediate layer with alarger diameter than the pipe 70 whereby the opposed sections 78, 78cannot be overlapped. The degrees of freedom in the diameter dimensionbecome large. Even when the opposed sections 78, 78 are overlapped inadvance, or when the section does not sufficiently overlap and the gap79 is partly generated, it is prevented for gas or liquid to penetratefrom the gap 79, since the gap 79 is sealed by a seal piece 77.

According to another example shown in FIG. 26 (B), the opposed sections78, 78 are caused to directly overlap to provide an overlapping section6. A separate seal piece 77 is positioned over the overlapping section 6and the seal piece 51 and the section 6 are integrally welded together.In this manner, even when the slit or the like is formed on the lappingportion 6, it is possible to keep impermeability and to furtherstrengthen the joint of the opposed sections 78, 78 at the overlappingsection 6. Forming of the overlapping section using the seal piece 77 isalso available for the bending treatment within the extrusion head. Inthe case, the opposed sections 78, 78 are made as the long side sections8, 8.

Preferred embodiments of the present invention relating to a step-lessstructure will now be described with reference to the accompanyingdrawings. FIG. 27 through FIG. 30 are drawings relating to the twelfthembodiment.

As shown in FIGS. 27 and 28, the rubber hose 1 is provided with anintermediate layer 2, an inner rubber layer 3 and an outer rubber layer2. The total thickness of the rubber hose including the intermediatelayer 2, the inner rubber layer 3 and the outer rubber layer 4 is about1.5˜3.5 mm. This is an extremely thin hose compared with a conventionalone.

Either the bending treatment within the extrusion head or the bendingtreatment outside the extrusion head can form the intermediate layer 2.The bending treatment within the extrusion head will now be described.The resin film 5 forming the intermediate layer 2 is rounded into acylindrical form to provide a partially overlapping section 6. Theoverlapping section 6 is provided with a thinned section 90 in thelongitudinal direction.

This simultaneous extrusion molding can be done by the above-describedmethod. The cross head structure is also available. A followingexplanation relates to the simultaneous extrusion molding.

FIG. 29 is a cross-sectional view of the intermediate layer 2 formed incylindrical shape and FIG. 30 is a partially extended perspective viewof the resin film 5 in a condition of a planar shape. As is obvious fromthese figures, the long side sections 8, 8 are respectively providedwith a thinned section 90 consisting of thin steps that are inverselyprovided. This thinned section 90 is formed to stretch over the fulllength of the resin film 5 in the width of the overlapping measurement(a) and continuously formed at the same time as molding of the resinfilm 5. Slits 7 are provided along the long side section 8 in a range,entering inwardly, forming a width of an overlapping dimension (a) fromeach edge section of both long side sections 8, 8 on the right and leftside. This overlapping dimension (a) has a width equivalent to orsmaller than that of the overlapping section 6. The structure of thelong side sections 8, 8 forming the thinned section 90 is one specificexample of a weak section structure.

The right and left thinned sections 90 are set to overlap at theoverlapping section 6. When a length obtained by adding one third (⅓) ofthe circumferential length of the intermediate layer 2 to thecircumferential length is set as the maximum width (i.e. short sidemeasurement) of the resin film 5 (for example, when the inner diameterof a rubber hose is 36.5 mm and the thickness thereof is 3 mm, the addedmeasurement is 41 mm), it is desirable that the thinned sections 7 of amaximum length of 40 mm be provided over an equal width in thelongitudinal direction of the resin film 5 on both sides or one side ofthe long side sections 8, 8 of the resin film 5.

In FIG. 30, when the thickness of the resin film 5 in a central section(a section between the long side sections 8, 8) in the lateral directionis T, one of the thinned sections 7 has a thickness t 1. The thicknessof the other thinned section 7 is t 2 where t 2=T−t 1. In this manner,both the thinned sections 90, 90 overlap at an overlapping section 6 sothat the total thickness becomes the thickness T of the resin film 5 atthe central section. Accordingly, the entire thickness is constant andno step is formed on the circumferential section of the intermediatelayer 2.

Operation of the present embodiment will now be explained. In FIG. 30,since the long side sections 8, 8 are provided with thinned sections 90,these sections 8, 8 form weak sections. Accordingly, when the resin film5 is bending-treated within the extrusion head, it is easily bent and auniform cylindrical shape can be provided. As a result, since a uniformcylindrical shape can be maintained even during the simultaneousextrusion molding in an extrusion head 10, it is possible to form a thinhose.

Accordingly, as no bar-shaped step resulting from the overlappingsection 6 is provided on the inner surface or outer surface of the thinrubber hose 1 after extrusion molding, the fastening force becomesconstant when the rubber hose 1 is mounted on the other member andsecured by a spring clip, and the sealing properties are improved. Thus,it is possible to make it difficult for the rubber hose 1 to separatefrom the other member. If the bar-shaped step is formed on the surface(i.e. outer surface) of the rubber hose 1, the fastening force of thespring clip becomes inconstant and thus an improved method of mountingis required to improve the sealing properties and non-separationproperties. Accordingly, the thin hose is realized without spoilingmounting performance.

Even in the case of woven fabric reinforced cloth which is superior tothe resin film in flexibility and extensibility and of which the clothend section in the overlapping section is originally difficult to breakduring extrusion molding, there is some possibility that the cloth endsection will break if the overlapping width is too great. In the case ofthe resin film that is inferior to the woven fabric reinforced cloth inflexibility and extensibility, it is considered that a break will beeasily generated in the course of bending into a cylindrical shape froma planar shape. However, by providing a thinned section 90, 90 on thelong side sections 8, 8, the resin film can be easily bent and such abreak is easily prevented. If the thinned sections 90, 90 are providedwith slits or the like, it is possible to make them weaker.

In a condition of the raw rubber hose obtained by such simultaneousextrusion molding, at the overlapping section 6 of the resin film 5forming the intermediate layer 2, the long side sections 8, 8 whichoverlap are not integrally secured by welding or the like. Accordingly,some displacement is possible between the overlapped sections.

However, since the intermediate layer 2 is integrally embedded betweenan inner rubber layer 3 and an outer rubber layer 4, it is possible tomaintain the overlapping section 6 even though there is deformation dueto a certain amount of displacement or the like. The overlappingmeasurement (a) (see FIG. 5) is also set to such a degree that theoverlapping section 6 can be maintained.

When the raw rubber hose 12 is vulcanized, it can be mounted on themandrel conforming to the bent shape of the latter since the overlappingsection 6 is designed to have a flexible structure for permittingdeformation such as displacement.

Next, when the raw rubber hose 12 mounted on the mandrel is vulcanizedat a predetermined temperature, the inner rubber layer 3 and the outerrubber layer 4 are vulcanized and set in a bent shape. Since the resinfilm 5 of the intermediate layer 2 is also melted at the vulcanizingtemperature and then hardened, the upper and lower long side sections 8,8 are integrally welded at the overlapping section 6. In this case,since the thinned sections 90 have disappeared to form a single resinlayer, impermeability improves further.

Further, if the resin film 5 is formed to have a multilayered structureof two to five layers and the melting point of the resin film of atleast an innermost layer or an outermost layer is lower than thevulcanizing temperature of the raw rubber hose, it is possible to weldthe overlapping section 6 and the thinned sections 90 of the resin film5 in the vulcanizing process. When a resin of which the permeabilityresistance is superior but the melting point is low is used, a resinwith a low melting point can also be used by laminating a resin, ofwhich the heat resistance is superior, to both sides of the resin with alow melting point.

FIGS. 31 and 32 relate to a thirteen embodiment, wherein FIG. 31 is anexplanatory view in the case where a resin film 5 is bent into acylindrical shape and FIG. 32 is partial cross-sectional view of anextrusion head 10. A structure of the extrusion head 10 shown in FIG. 32is as same as one shown in FIG. 11. In FIG. 31, the upper section of thefigure shows the resin film in an extended shape where the long sidesections 8, 8 are provided with inversely faced tapered surfaces 91, 91,thereby forming the thinned sections 90, 90. The tapered surfaces 91, 91are formed in an inclined shape so that the thinned sections 90, 90 aregradually thinned toward one end in the lateral direction of the longside sections 8, 8.

As shown in the lower section of the figure, when the resin film 5 isrounded in the lateral direction to allow the long side sections 8, 8 tooverlap, the taper surfaces 91, 91 overlap to provide an overlappingsection 6. When the thickness of the resin film 5 in a central section(a section between the long side sections 8, 8) in the lateral directionis T, the thickness of the overlapping section 6 is almost equivalent toT. As a result, it is possible to dispense with any step on theoverlapping section 6.

The taper surfaces 91, 91 can be provided on the surface of the longside sections 8, 8 opposing one another or on the surface on the sameside. The taper surfaces 91, 91 can also be provided to form a wedge inthe cross-section from both surfaces. Further, the tapered sections 91,91 can be formed to stretch the full length of the resin film 5 in thelongitudinal direction in the width of the overlapping measurement (a)and can be continuously formed at the same time as molding of the resinfilm 5 or formed in the subsequent process.

It is desirable that the length of the taper surfaces 91, 91 in eachlateral direction be longer by a predetermined measurement (e.g. about10 mm) than the length (a) of the overlapping section 6. In this manner,even though the length of the overlapping section 6 has changed minutelyat the time of actual extrusion molding, it is possible to sufficientlysecure the thickness as the intermediate layer 2 to maintain a necessarylevel of permeability resistance. Even though the overlapping section 6has been displaced a little in the lateral direction, it is possible tosubstantially make the entire thickness of the overlapping section 6constant so that a bar-shaped step resulting from the overlappingsection 6 is not produced on the inner surface or outer surface of thethin rubber hose 1.

In particular, in the intermediate layer 2 with a thickness of 0.05 mmor more, when a step corresponding to the thickness of the film isproduced at the overlapping section 6, even though the overlappingsection 6 is covered by the inner and outer rubber layers, the steptends to remain on the inner surface of the inner layer or the outersurface of the outer layer. The greater the thickness of the film andthe greater the elasticity, the more prominent the step, and the thinnerthe inner and outer rubber layers, the more prominent the step. However,by making the long side sections 8, 8 thinner and tapered, it ispossible to substantially remove such a step. It is also possible toprovide slits on the thinned section to make it weaker for easy bending.

To form the resin film 5 in a cylindrical shape, as shown in FIG. 32, anintermediate layer passage 12 is provided between an outer die 27 and aninner die 28 within an extrusion head 10. The resin film 5 is roundedand inserted into the intermediate layer passage 12. The intermediatelayer passage 12 is a ring-shaped space and the opening width is almostthe same as the thickness of the overlapping section 6.

The upper and lower long side sections 8, 8 forming the overlappingsection 6 partially contact the inside of the intermediate layer passage12. However, space 29 is formed between a part of the overlappingsection 6 and parts other than the overlapping section 6 and theintermediate layer passage 12. When operation of a vacuum pump 26connected through the space 29 to the intermediate layer passage 12reduces the pressure of the intermediate layer passage 12, the pressureof the space between the upper and lower long side sections 8, 8 is alsoreduced at the overlapping section 6. As a result, the upper and lowerlong side sections 8, 8 are caused to closely contact each other.

In this condition, an inner rubber layer 3 and an outer rubber layer 4are extruded inside and outside the resin film 5 for integration.Accordingly, even though the resin film 5 is too hard to allow closecontact with the overlapping section 6, it is possible to allow reliablecontact with the overlapping section and to perform simultaneousextrusion molding. It is also possible to efficiently mass-produce arubber hose. In addition, since foreign materials such as volatilematter in the overlapping section 6 are extracted and removed, it ispossible to prevent a phenomenon whereby the volatile matter expands toform bubbles during heating in the subsequent vulcanizing process.

A stepless structure is provided, in which the long side sections 8, 8are thinned in the tapered shape as shown in the present embodiment orthe long side sections 8, 8 are thinned in the step shape as shown inFIG. 30, so that the thickness of the overlapping section 6 is the sameas or equivalent to that of the non-overlapping sections, therebyproviding the overlapping section 6 without any step or with a smallstep. This stepless structure can not only be applied to the moldingmethod according to the previous embodiment in which the longbelt-shaped film 5 is rounded to be inserted into the extrusion head,thereby forming the cylindrical shape, but also to a production methodin which the film is rounded into the cylindrical shape in advance infront of the extrusion head or the film is extrusion-molded first as apipe member, and then slits are formed on the pipe member in thelongitudinal direction for opening the pipe member (referred to as“preforming treatment”).

FIG. 33 is a fourteenth embodiment further showing another example foreliminating the step in the overlapping section 6. In this example, theoverlapping section 6 of a general structure provided with a step D isformed in a cylindrical shape (see FIG. 23A). The step D is then meltedby means of ultrasonic welding or the like to eliminate at least thestep formed on the outer surface side (see FIG. 23B). In this manner,since the same degree of accuracy in overlapping is not required as inthe case where a side of the resin film 5 is thinned in advance beforeoverlapping, production becomes easier.

When a rubber hose according to the present invention is molded eitherby a cross head structure method, by a helically winding or by aoverlapping section, which is parallel to the axis line, forming method,the overlapping portion can be made to be the step-less structure. In acase in which the bending treatment outside the extrusion head isadopted, the thinned portion can be formed during the resin pipe issupplied to the extrusion head while pressure is reduced after the pipeis formed in advance in a cylindrical shape and cut out along thelongitudinal direction. It is possible to form a cut out portion in athinned portion simultaneously with the extrusion of the pipe and thethin portion is formed simultaneously with cutting out.

INDUSTRIAL APPLICABILITY

Production method of a thin rubber hose according to the presentinvention is suitable for thinning a impermeability rubber hose for thepurpose of light-weighting and cost reduction and for extrusion moldingof gas or liquid transportation hose using a resin or metal film as anintermediate layer for improving permeability performance.

1. A method for producing by extrusion molding a thin rubber hose havinga resin film as an intermediate layer with an inner rubber layer and anouter rubber layer laminated inside and outside the resin film, theresin film consisting of a long belt-shaped film having a weak sectionprovided in advance on the long sides of the film, wherein the resinfilm is rolled up into a cylindrical shape so that the two long sidesoverlap, comprising the steps of: feeding a long, belt-shaped resin filmof which the long sides are provided with a weak section in advance intoan extrusion head to be rolled up and bent into a cylindrical shape sothat the two long sides overlap; extruding rubber inside and outside theresin film for integration and extrusion-molding a raw rubber hose ofwhich the intermediate layer is the resin film; and heating the rawrubber hose to a predetermined temperature for vulcanization.
 2. Themethod for producing the thin rubber hose according to claim 1, whereinthe resin film is a thermoplastic resin and the overlapping section isintegrally welded simultaneously with vulcanization.
 3. The method forproducing the thin rubber hose according to claim 1, wherein the weaksection is composed of a plurality of slits cut inwardly from the edgesections of the long sides, and the inward end of each slit is inclinedtoward the feeding direction of the resin film or is providedperpendicular to the longitudinal direction of the resin film.
 4. Themethod for producing the thin rubber hose according to claim 3, whereinthe slits are respectively provided on both long sides and provided in apositional relation in which they do not overlap when the two long sidesoverlap.
 5. The method for producing the thin rubber hose according toclaim 3, wherein the slits are respectively provided on the two longsides in a positional relation in which they overlap when the two longsides overlap.
 6. The method for producing the thin rubber hoseaccording to claim 1, wherein the weak section is composed of aplurality of punched holes.
 7. The method for producing the thin rubberhose according to claim 1, wherein the weak section is formed bythinning one or both of the long side sections which overlap.
 8. Themethod for producing the thin rubber hose according to claim 1, whereinthe rubber is mixed with a thermoplastic resin and after vulcanizing theraw rubber hose, this hose is reheated to about the melting temperatureof the mixed thermoplastic resin to give a predetermined shape.
 9. Themethod for producing the thin rubber hose according to claim 7, whereinthinning is realized by a taper shape in which the thickness isgradually reduced toward an end section.
 10. A method for producing athin rubber hose by extruding an inner layer rubber and an outer layerrubber inside and outside an intermediate layer made of a film of asubstantially cylindrical shape, comprising the steps of: rolling abelt-shaped film into a substantially cylindrical shape to allow a pairof edge sections, one on each side in the lateral direction of the film,to overlap to form an overlapping section and feeding the film into anextrusion head; and extruding the inner layer rubber and the outer layerrubber inside and outside the film while decompressing and drawing theoverlapping section within the extrusion head.
 11. The method forproducing a thin rubber hose which has an intermediate film layeraccording to claim 10, wherein the film is fed into the extrusion headwhile being rolled up from a planar shape to a substantially cylindricalshape at the inlet of the extrusion head.
 12. The method for producing athin rubber hose which has an intermediate film layer according to claim10, wherein the film is shaped into a substantially cylindrical shape inadvance before fed into the extrusion head.
 13. The method for producinga thin rubber hose which has an intermediate film layer according toclaim 10, wherein the film is composed of a thermoplastic resin or aninorganic material such as metal, or a laminated structure combiningthem.
 14. The method for producing a thin rubber hose which has anintermediate film layer according to claim 10, wherein the film bendingload is 400 N or more when the film width is 100 mm and the filmthickness is 0.05 mm.
 15. The method for producing a thin rubber hoseaccording to claim 10, wherein each of the pair of edge sectionsoverlapping at the overlapping section is tapered so that they arethinned toward the end in the lateral direction thereof.
 16. A methodfor producing a thin rubber hose provided with an intermediate layer byextruding an inner rubber layer and an outer rubber layer inside andoutside the intermediate layer of a substantially cylindrical shapewithin an extrusion head, comprising the steps of: forming a pipeserving as the intermediate layer in advance; providing the pipe with acut line in the axial direction; feeding the pipe into the extrusionhead, cutting the pipe open; and rounding the pipe again within theextrusion head to allow the cut line sections to directly or indirectlyoverlap, thereby forming the cylindrical-shaped intermediate layer. 17.The method for producing a thin rubber hose provided with anintermediate layer according to claim 16, wherein the bending load ofthe intermediate layer is 400 N or more for a film of 100 mm width and0.05 mm thickness.
 18. The method for producing a thin rubber hoseprovided with an intermediate layer according to claim 16, wherein theinner rubber layer and the outer rubber layer are extruded,decompressing and drawing in the overlapping section.
 19. The method forproducing a thin rubber hose provided with an intermediate layeraccording to claim 16, wherein the intermediate layer is formed in abellows-shape.
 20. A method for producing by extrusion molding a thinrubber hose having an inner rubber layer and an outer rubber layerlaminated respectively inside and outside a resin film serving as anintermediate layer, the intermediate layer having a circular crosssection and forming an overlapping section by allowing a pair of sidesections, which divide the intermediate layer in the circumferentialdirection, to overlap, wherein at least one of the two sides forming theoverlapping section on the surface side is thinned to eliminate a stepin the overlapping section on the surface side, comprising the steps of:thinning at least one of two long side sections of a long belt-shapedresin film; rounding the resin film to be fed into an extrusion head sothat the two long sides of the resin film overlap to form an overlappingsection where no step is produced at least on the surface side; bendingthe resin film into a cylindrical shape within the extrusion head; andextruding rubber inside and outside the resin film.
 21. A method forproducing by extrusion molding a thin rubber hose having an inner rubberlayer and an outer rubber layer laminated respectively inside andoutside a resin film serving as an intermediate layer, the intermediatelayer having a circular cross section and forming an overlapping sectionby allowing a pair of side sections, which divide the intermediate layerin the circumferential direction, to overlap, wherein at least one ofthe two sides forming the overlapping section on the surface side isthinned to eliminate a step in the overlapping section on the surfaceside, comprising the steps of: rounding a long belt-shaped resin film toallow the two long side sections to overlap; forming the resin film intoa cylindrical shape which has an overlapping section where a step isproduced at least on the surface side; eliminating the step on thesurface side by a subsequent process; and extruding rubber inside andoutside the cylindrical resin film.